Solventless or high solids-containing silicone pressure sensitive adhesive compositions

ABSTRACT

Solventless or low solvent-containing silicone pressure sensitive adhesive compositions having excellent adhesive strength and high tack are provided, comprising (A) a toluene-soluble resinous copolymer containing R 3  SiO 1/2  units and SiO 4/2  units; (B) a vinyi-endblocked polydiorganosiloxane having a viscosity of 10 to 500 centipoise at 250° C.; (C) a hydride-endblocked polydiorganosiloxane having a viscosity of 10 to 1,000 centipoise at 250° C.; the ratio of silicon-bonded hydrogen atoms in (C) to olefinically unsaturated radicals in the total of (A) and (B), being in the range of from about 1.2:1 to about 15.0:1; and (D) a hydrosilation catalyst.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to the concurrently file applications identified asAttorney Docket Nos. 60SI-1449 and 60SI-1455, also known as Ser. No.07/675,398 filed Mar. 26, 1991, now U.S. Pat. No. 5,190,827, issued Mar.2, 1993, and Ser. No. 07/675,380, filed Mar. 26, 1991 pending.

BACKGROUND OF THE INVENTION

The present invention relates to silicone compositions suitable forforming pressure sensitive adhesive compositions. More particularly, thepresent invention relates to solventless or high solids-containing,addition-curable silicone compositions suitable for forming pressuresensitive adhesive compositions having excellent tack and adhesiveproperties.

The term "pressure sensitive adhesive" (PSA) as used herein refers toadhesives that can be adhered to a surface and yet can be stripped fromthe surface without transferring more than trace quantities of adhesiveto the surface, and can be readhered to the same or another surfacebecause the adhesive retains some or all of its tack and adhesivestrength.

Silicone pressure sensitive adhesives have excellent adhesive andcohesive strength and high tack as well as excellent heat resistance,cold resistance, electrical properties, and the like, which makes themapplicable for use as electrical-insulating tape and for variouspressure-sensitive products which must be resistant to hot and cold.

However, a drawback associated with silicone pressure sensitiveadhesives is the use, handling, and emission of flammable and volatileorganic compounds, e.g., organic solvents, in the preparation of thepressure sensitive adhesives from compositions containing high levels oforganic solvent. Conventional pressure sensitive adhesives are madeusing high viscosity vinyl polymer inputs. Solvent is generally used forthe purpose of reducing the viscosity of the composition to a levelwhich renders the curable composition processable. It would be desirableto provide solventless or high solids containing (i.e., lowsolvent-containing) pressure sensitive adhesive silicone compositionscontaining low viscosity vinyl polymer inputs.

Addition-curable, low solvent-containing silicone compositions capableof curing to form pressure sensitive adhesive compositions are known inthe art.

U.S. Pat. No. 3,983,298 (Hahn et al.) is directed to a siliconecomposition suitable for use as a pressure sensitive adhesive andobtained by mixing components consisting essentially of (a) 50-60 partsby weight of a solid, benzene-soluble resin copolymer consistingessentially of R₃ SiO_(1/2) units and SiO_(4/2) units, which is known asan "MQ" resin, (b) 40-50 parts by weight of a vinyl-terminatedpolydiorganosiloxane having a viscosity of from 20,000 to 100,000centistokes at 250° C., (c) a hydrogen-containing organopolysiloxane inan amount sufficient to provide from 1.0 to 20.0 silicon-bonded hydrogenatoms for every olefinically unsaturated radical in the total of (a)plus (b), and (d) a platinum-containing catalyst. It is pointed out inHahn et al. that compositions of the prior art based on mixtures of abenzene soluble resin copolymer containing R₃ SiO_(1/2) units andSiO_(4/2) units (hereinafter sometimes referred to as "MQ resin") andlow viscosity silicones do not form pressure sensitive adhesivecompositions.

U.S. Pat. No. 4,774,297 (Murakami et al.) is directed to a compositionsuitable for forming a pressure sensitive adhesive having excellent tackand adhesive strength, comprising (A) 30-70 parts by weight of avinyl-terminated polydiorganosiloxane having a viscosity of at least500,000 centistokes at 250° C., (B) 70-30 parts by weight of anorganopolysiloxane containing R₃ SiO_(1/2) units and SiO_(4/2) units,(C) an organohydrogensiloxane in an amount sufficient to provide 1-20silicon-bonded hydrogen atoms per alkenyl group, (D) aplatinum-containing catalyst, and (E) from 25-400 parts by weight of anorganic solvent. The vinyl polymer used in the Murakami et al.composition has a viscosity of at least 500,000 centistokes andpreferably at least one million centistokes at 250° C.

European Patent Application No. 0269454 (Murakami et al.) discloses acomposition suitable for forming a pressure sensitive adhesive havingexcellent tack and adhesive strength and comprising an alkenylgroup-containing silicone polymer, a tackifying silicone resin, anorganohydrogensiloxane, and a platinum-containing catalyst. There issaid to be no specific restriction on the molecular weight of thealkenyl group-containing silicone polymer as long as no adverse effectaccrues with respect to the workability of the pressure sensitiveadhesive composition. If the pressure sensitive adhesive composition issolventless, the viscosity of the alkenyl group-containing siliconepolymer is no more than 100,000 centistokes at 250° C., while in asolvent-containing composition, the alkenyl group-containing siliconepolymer should have a viscosity of at least one million centistokes at250° C. The organo-hydrogenpolysiloxane should be present in an amountsufficient to provide 1 to 40 silicon-bonded hydrogen atoms per alkenylgroup in the composition. The Murakami et al. reference does notdisclose a pressure sensitive adhesive composition prepared with lowviscosity vinyl-functional silicones.

U.S. Pat. No. 4,988,779 (Medford et al.) discloses a composition havinga solvent content of no more than 5-10% by weight and suitable forforming a pressure sensitive adhesive, wherein the composition comprisesfrom 30 to 50 parts of a vinyl endblocked polydiorganosiloxane fluidhaving a viscosity of from 500 to 10,000 centistokes at 250° C., from 50to 70 parts of a benzene soluble resin copolymer containing R₃ SiO_(1/2)units and SiO_(4/2) units, an organopolysiloxane having silicon bondedhydrogen atoms, and a platinum catalyst. The hydrogen-containingorganopolysiloxane is present in an amount sufficient to provide from1.0 to 30.0 silicon bonded hydrogen atoms for every olefinicallyunsaturated radical in the composition.

European Patent Application No. 0355991 (Boardman) is directed to apressure sensitive adhesive composition having a high solids content,i.e., typically in excess of 95% by weight, preferably in excess of 98%by weight, comprising (a) an MQ resin containing silicon-bonded hydroxylradicals ranging from 1 to 4 percent by weight of the copolymer, (b) analkenyl-terminated polydiorganosiloxane, (c) a hydrogen-terminatedpolydiorganosiloxane, (d) a crosslinking agent, and (e) a hydrosilationcatalyst. The number of repeating units in the alkenyl-terminatedpolydiorganosiloxane and the hydrogen-terminated polydiorganosiloxaneranges from 0 to 1,000 in each. The crosslinking agent is anorganosiloxane containing more than two groups that will condense with ahydrogen or alkenyl group of an organopolysiloxane in a hydrosilationreaction. The ratio of the total number of silicon-bonded alkenyl groupspresent in (d) and (b) to the total number of silicon-bonded hydrogenatoms present in (d) and (c) ranges from 0.8 to 1.2, i.e., the ratio ofthe total number of silicon-bonded hydrogen atoms in (d) and (c) to thetotal number of silicon-bonded alkenyl groups in (d) and (b) ranges from0.83-1.25:1. The Boardman composition contains an external crosslinkingagent. In the examples in Boardman,1,3,5,7-tetravinyl-tetramethyl-cyclotetrasiloxane is used as thecrosslinker. The results reported in the examples show that the tackobtained therein ranged from low to moderate.

It is desirable to provide solventless or high solids-containingpressure sensitive adhesive compositions containing polymer inputshaving viscosities lower than those taught in the prior art. It isfurther desirable to provide solventless or high solids containingpressure sensitive adhesive compositions which cure to form pressuresensitive adhesives having high tack values as well as high peeladhesion values.

Such silicone pressure sensitive adhesive compositions are provided bythe present invention.

SUMMARY OF THE INVENTION

The present invention is directed to a solventless or highsolids-containing organopolysiloxane composition curable to produce apressure sensitive adhesive having high tack and high peel adhesionproperties, comprising by weight:

(A) from about 50 to about 75 parts by weight of a toluene soluble,resinous copolymer comprising R₃ SiO_(1/2) units and SiO_(4/2) unitswherein R is a monovalent hydrocarbon radical having from 1 to about 6carbon atoms, wherein the resinous copolymer comprises from about 0.2%to about 5.0% by weight, based on the total weight of the copolymer, ofhydroxyl radicals, at least 95% of all R groups being an alkyl group,the total number of R radicals that are alkenyl radicals being 0-0.5% ofall R radicals, the molar ratio of R₃ SiO_(1/2) units to SiO_(4/2) unitsbeing from about 0.6 to about 0.9 inclusive;

(B) an alkenyl-terminated polydiorganosiloxane having a viscosity offrom about 10 to about 500 centipoise at 250° C. and having the generalformula

    R.sup.2 R.sup.1.sub.2 SiO(R.sup.3.sub.2 SiO).sub.m SiR.sup.1.sub.2 R.sup.2 ( 1)

wherein each R¹ is independently an alkyl group having from 1 to about10 carbon atoms or an aryl group, R² is an alkenyl group having from 1to about 10 carbon atoms, each R³ is independently R¹ or R², with theproviso that at least 99.5% of all R³ radicals are R¹, and "m" is anumber in the range of from about 1 to about 300;

(C) a hydride-terminated organohydrogenpolysiloxane compatible with themixture of (A) and (B) and having a viscosity of from about 10 to about1,000 centipoise at 250° C. and having the general formula

    R.sup.4.sub.2 HSiO(R.sup.5.sub.2 SiO).sub.a SiHR.sup.4.sub.2 ( 11)

wherein each R⁴ is independently an alkyl group having from 1 to about10 carbon atoms or an aryl group, and each R⁵ iS hydrogen or R⁴, withthe proviso that at least 99.5% of all R⁵ radicals are R⁴, "a" is anumber in the range of from 1 to about 500, there being at least twosilicon-bonded hydrogen atoms per molecule of (C), no silicon atombearing more than one silicon-bonded hydrogen atom; the total of (B) and(C) being from about 25 to about 50 parts by weight; the total of (A),(B), and (C) being 100 parts by weight; the molar ratio ofsilicon-bonded hydrogen groups in (C) to silicon-bonded alkenyl groupsin (A) and (B) being in the range of from about 1.2:1 to about 15.0:1;

(D) a catalytic amount of a hydrosilation catalyst; and

(E) from 0 to about 40% by weight of an organic solvent.

The present invention is based on the discovery that a solventless orhigh solids-containing pressure sensitive adhesive composition havinghigh tack and high peel adhesive properties can be obtained from lowviscosity vinyl polymer inputs by (1) first effecting a hydrosilationreaction between (A), (B) and (C) in the presence of (D), wherein themolar ratio of silicon-bonded hydrogen groups in (C) to silicon-bondedalkenyl groups in (B) (sometimes referred to herein as the "SiH:SiVinyl"ratio) is within a critical range, and further wherein the hydroxycontent of the resinous copolymer (A) is at a critical level, and (2)then effecting a condensation reaction between the hydroxyl radicals onthe resinous copolymer (A) and the excess terminal hydride radicals on(C).

The compositions of the present invention provide several advantages.They cure to form pressure sensitive adhesives having a tack of greaterthan 200 grams/cm², preferably greater than 700 grams/cm² ; a peeladhesion strength greater than 25 ounces/inch, preferably greater than30 ounces/inch. The compositions of this invention are prepared from lowviscosity vinyl polymers and require no solvent to improve workabilityin the uncured state. Furthermore, the compositions of this inventioncan cure fast at low temperatures to produce pressure sensitiveadhesives having superior properties.

Other aspects of this invention are directed to pressure sensitiveadhesives made from the curable compositions of this invention and to amethod for preparing the pressure sensitive adhesives.

DETAILED DESCRIPTION OF THE INVENTION

Component (A) of the composition of the present invention is atoluene-soluble resinous organopolysiloxane copolymer which imparts tackto the cured pressure sensitive adhesive prepared from the composition.The resinous copolymer (A) comprises R₃ SiO_(1/2) units (also known as"M" units) and SiO_(4/2) units (also known as "Q" units) wherein R is amonovalent hydrocarbon radical having from 1 to about 6 carbon atoms.Examples of radicals represented by R include alkyl radicals such asmethyl, ethyl, and isopropyl; cycloaliphatic radicals such ascyclopentyl and cyclohexenyl; olefinic radicals, such as vinyl andallyl; and the phenyl radical. At least 95% of all R groups are alkylgroups, preferably methyl. The total number of R radicals that arealkenyl radicals being 0-0.5% of all R radicals. The molar ratio of R₃SiO_(4/2) units to SiO_(4/2) units is from about 0.6 to about 0.9inclusive. The resinous copolymer comprises from about 0.2% to about5.0% and preferably from about 1.0 to about 3.0%, and most preferablyfrom about 1.5% to about 2.5%, by weight based on the total weight ofthe copolymer, of hydroxyl radicals. The hydroxyl radicals are bondeddirectly to the silicon atom of the SiO_(4/2) units or of the R₃SiO_(1/2) units or some of the hydroxyl radicals can be bonded directlyto the silicon atom of the SiO_(4/2) units and some of the hydroxylradicals can be bonded directly to the silicon atom of the R₃ SiO_(1/2)units.

(A) is present in the composition of this invention in an amount withinthe range of from about 50 to about 75, preferably from about 50 toabout 70, and most preferably from about 55 to about 62, parts byweight.

Methods for making the resinous copolymer (A) are known in the art.Reference is made, for example, to U.S. Pat. No. 2,676,182 to Daudt etal., which is hereby incorporated by reference herein. In the Daudt etal. method, a silica hydrosol is reacted under acidic conditions with asource of triorganosiloxy units such as a hexaorganodisiloxane, e.g.,hexamethyldisiloxane, or a hydrolyzable triorganosilane, e.g.,trimethylchlorosilane, or mixtures thereof, and recovering a benzenesoluble resin copolymer having M and Q units.

The resinous copolymer (A) is a solid, resinous material and is mostoften available as a solution in a solvent such as xylene or toluene,generally as a 40% to 60% by weight solution. For ease of handling ofthe composition of the present invention, one part of the solution ofthe resinous copolymer is usually dissolved in some or all of the vinylchain-stopped polysiloxane (B) and the other part of the solution of theresinous copolymer is usually dissolved in some or all of the hydridechain-stopped polysiloxane (C) and the solvent stripped from each of theresulting solutions to produce solutions of resinous copolymer (A) inthe vinyl-chainstopped polysiloxane (B) and in the hydride-chainstoppedpolysiloxane (C). The solution of (? N) and (B) typically contains fromabout 50 to about 75, preferably from about 50 to about 70, and mostpreferably from about 55 to about 62, parts by weight, of (A), and fromabout 25 to about 50, preferably from about 30 to about 50, and mostpreferably from about 38 to about 45 parts by weight, of (B). Thesolution of (A) and (C) typically contains from about 50 to about 75,preferably from about 50 to about 70, and most preferably from about 55to about 62, parts by weight, of (A), and from about 25 to about 50,preferably from about 30 to about 46, and most preferably from about 38to about 45 parts by weight, of (C).

Component (B) of the composition of the present invention is analkenyl-terminated polydiorganosiloxane having the general formula

    R.sup.2 R.sup.1.sub.2 SiO(R.sup.3.sub.2 SiO).sub.m SiR.sup.1.sub.2 R.sup.2 ( 1)

wherein each R¹ is independently an alkyl group having from 1 to about10 carbon atoms or an aryl group, R² is an alkenyl group having from 1to about 10 carbon atoms, each R³ is independently R¹ or R², with theproviso that at least 99.5% of all R³ radicals are R¹, and "m" is anumber in the range of from about 1 to about 300.

In formula (1), R¹ is an alkyl group having from 1 to about 10 carbonatoms such as methyl, ethyl, and propyl; or aryl group such as phenyl.Preferably, at least 95 percent and most preferably 100 percent of allR¹ radicals are alkyl and most preferably methyl. R² is an alkenyl groupsuch as vinyl, allyl, propenyl, or hexenyl. Preferably, R² is vinyl.Each R³ is either R¹ or R², with the proviso that at least 99.5%, andpreferably 100%, of all R³ radicals are R¹. Like R¹, R³ is preferably analkyl group having from 1 to about 10 carbon atoms, and most preferablymethyl. The presence of silicon-bonded alkenyl groups on the internalsilicon atoms of the polymer chain of formula (1) constitute impuritieswhich are preferably minimized or avoided.

In formula (1), "m" represents a number from about 1 to about 300,preferably from about 20 to about 250, and most preferably from about 60to about 200.

The viscosity of the alkenyl-terminated polydiorganosiloxane (B) rangesfrom about 10 to about 500, preferably from about 20 to about 400, andmost preferably from about 100 to about 300, centipoise at 250° C.

Alkenyl-terminated polydiorganosiloxanes (B) can be prepared by any ofthe conventional methods for preparing triorganosiloxane-terminatedpolydiorganosiloxanes. For example, a proper ratio of the appropriatehydrolyzable silanes, e.g., vinyldimethylchlorosilane anddimethyldichlorosilane, may be cohydrolyzed and condensed or alternatelyan appropriate 1,3-divinyltetraorganodisiloxane, e.g., symmetricaldivinyldimethyldiphenyidisiloxane or divinyltetramethyidisiloxane, whichfurnishes the endgroups of the polydiorganosiloxane, may be equilibratedwith an appropriate diorganopolysiloxane, e.g.,octamethylcyclotetrasiloxane, in the presence of an acidic or basiccatalyst. Regardless of the method of preparation ofpolydiorganosiloxane (B), there is usually coproduced a varying quantityof volatile, cyclic polydiorganosiloxanes. Volatile cyclicpolydiorganosiloxanes, e.g., methyl tetramer, should be removed, sincethey are volatile and adversely affect pressure sensitive adhesiveproperties.

The amount used of polydiorganosiloxane (B), its formula (presentedhereinabove as formula (1)), and its viscosity, for the purposes of thisinvention, refers to the essentially cyclic free portion of thepolydiorganosiloxane. This essentially cyclic free portion can bedetermined by heating a sample of the polydiorganosiloxane at 150° C.for up to 1 hour to yield a residue. This residue will be essentiallyfree of cyclic material with the exception of trace quantities ofmacrocyclic polydiorganosiloxanes which are non-volatile at 150° C. andatmospheric pressure. Many of these polydiorganosiloxanes (B) arecommercially available. Furthermore, component (B) can be homopolymersor copolymers or their several mixtures as long as they arealkenyl-endblocked polydiorganosiloxanes of formula (1).

Component (C) is an organohydrogenpolysiloxane compatible with themixture of (A) and (B) and having the general formula

    R.sup.4.sub.2 HSiO(R.sup.5.sub.2 SiO).sub.a SiHR.sup.4.sub.2 ( 11)

wherein each R⁴ iS independently an alkyl group having from 1 to about10 carbon atoms or an aryl group, and each R⁵ iS hydrogen or R⁴, withthe proviso that at least 99.5%, and preferably 100%, of all R⁵ radicalsare R⁴.

The term "compatible" means that the required amount oforganohydrogenpolysiloxane (C) is at least partially soluble in themixture of (A) and (B) and will exist in a uniformly dispersed state inthe composition of this invention while participating in the curingreaction, until the cure has been effected.

Examples of alkyl groups represented by R⁴ and R⁵ in formula (11) aboveinclude methyl, ethyl, and propyl. An example of an aryl grouprepresented by R⁴ and R⁵ iS phenyl. R⁴ iS preferably an alkyl radicaland most preferably methyl. Preferably, at least 99.5 percent and mostpreferably 100 percent of all R⁵ radicals are alkyl and most preferablymethyl.

In formula (11), "a" is a number in the range of from 1 to about 500,preferably from about 20 to about 400, and most preferably from about 60to about 250.

The viscosity of (C) is from about 10 to about 1,000, preferably fromabout 20 to about 750, and most preferably from about 100 to about 400,centipoise at 250° C.

The total amount of (B) and (C) is from about 25 to about 50, preferablyfrom about 30 to about 50, and most preferably from about 38 to about45, parts by weight.

The molar ratio of silicon-bonded hydrogen groups (i.e., "SiH") in (C)to silicon-bonded alkenyl groups (i.e., "SiVinyl") in (B) and (A) is inthe range of from about 1.2:1 to about 15.0:1; preferably from about1.25:1 to about 6.0:1, and most preferably from about 1.35:1 to about4.5:1. The amount of (C) sufficient to fulfill these ratio requirementsis determined by measuring the alkenyl or vinyl contents of the desiredtypes and amounts of components (A) and (B), which is typically done bySilicone-29 NMR. A precise amount of (C) can be used to provide aspecific ratio of SiH to SiVinyl (also referred to herein as"SiH:SiVi").

It is critical to the present invention that the molar ratio ofsilicon-bonded hydrogen groups (i.e., sometimes referred to herein as"SiH") in (C) to silicon-bonded alkenyl groups (i.e., sometimes referredto herein as "SiVi") in (B) be in the ranges recited above. Maintainingan SiH:SiVi ratio within these limits ensures that a high molecularweight silicone network is formed during cure and ensures maximum tackvalues and thermal stability of the cured pressure sensitive adhesivedeveloped through additional reaction between the available excess SiHgroups with silanol groups of MQ resin..

The hydride polysiloxane (C) must be terminated with hydride groups sothat polymer chain extension with the terminal vinyl groups on (B) willoccur during cure.

Organohydrogenpolysiloxanes and their preparation are well known in theorganosilicon polymer art; some are commercially available. Briefly, thepreparation of organohydrogensiloxanes can be accomplished in anysuitable manner such as by hydrolyzing silanes, such as chlorosilanes,and equilibrating the resulting hydrolyzate under acid catalysis.Alternately, a mixture of suitable siloxanes, such as cyclic siloxanesand linear siloxanes, can be copolymerized and equilibrated under acidcatalysis. For example, a hydride-stopped silicone fluid suitable foruse in the present invention can be prepared by reactingtetramethyldisiloxane with cyclic methyl tetramer of predetermined ratioin the presence of Filtrol-20 as catalyst for 4-6 hours at 80°-100° C.The Filtrol-20 catalyst is then removed by filtration and the residualreactants are removed by vacuum stripping.

Component (D) of the composition of the present invention is a catalystwhich promotes the hydrosilation reaction. Useful catalysts forfacilitating the hydrosilation curing reaction include precious metalcatalysts such as those which use ruthenium, rhodium, palladium, osmium,iridium, and platinum, and complexes of these metals. Examples ofsuitable hydrosilation catalysts for use in the present invention aredisclosed, for example, in U.S. Pat. Nos. 3,159,601 and 3,159,662(Ashby); 3,220,970 (Lamoreaux); 3,814,730 (Karstedt); 3,516,946 (Modic),and 4,029,629 (Jeram); all of the foregoing patents being herebyincorporated by reference herein.

Preferably, the hydrosilation catalyst used in the present invention isa platinum-containing catalyst. Suitable platinum-containinghydrosilation catalysts include any of the well known forms of platinumthat are effective for catalyzing the reaction of silicon-bondedhydrogen atoms with silicon-bonded vinyl groups, such as finely dividedmetallic platinum, platinum on a finely divided carrier such as alumina,compounds of platinum such as chloroplatinic acid and complexes ofplatinum compounds.

Other suitable platinum-containing hydrosilation catalysts for use inthe present invention include the platinum hydrocarbon complexesdescribed in U.S. Pat. Nos. 3,159,601 and 3,159,662 to Ashby, and theplatinum alcoholate catalysts described in U.S. Pat. No. 3,220,970 toLamoreaux, as well as the platinum catalysts of U.S. Pat. No. 3,814,730to Karstedt. Additionally, the platinum chloride-olefin complexesdescribed in U.S. Pat. No. 3,516,946 to Modic are also useful herein.All of the aforesaid catalysts are thermally activated. Also useful arethe photoactive platinum catalysts such as those of U.S. Pat. No.4,510,094 to Drahnak. All of the U.S. Patents cited in the instantparagraph are incorporated by reference into the present disclosure.

Catalysts which are soluble in the mixture of (A), (B) and (C) arepreferred, particularly if optical clarity is desired.

The platinum-containing catalyst (D) is present in the composition ofthis invention in an amount sufficient to provide at least 0.1 part byweight platinum for one million parts by weight of the combined weightof (A), (B), and (C). Frequently, such small amounts of catalyst arepoisoned by trace amounts of impurities in the composition so it isadvantageous to use the platinum catalyst in such quantities to provideat least 1.0 part per million (ppm). The amount of platinum-containingcatalyst is not critical with respect to the upper limit but its costwould suggest that excessive quantites be avoided. Amounts of up to 200ppm platinum are not unusual but preferably from 1 to 35 parts by weightof platinum for every one million parts by weight of the total of (A),(B), and (C) is used.

The compositions of the present invention can further comprise fromabout 0 to about 40, preferably from about 0 to about 20, and mostpreferably about 0, percent by weight of an organic solvent (E).Suitable organic solvents include any of the solvents conventionallyused with organosiloxanes and having a boiling point below approximately250° C., such as aromatic hydrocarbons, e.g., benzene, toluene, andxylene; aliphatic hydrocarbons such as hexane, heptane, and cyclohexane;halogenated hydrocarbon solvents such as trichloroethane and chloroform;naphthas such as petroleum ether, VM and P Naphtha and refined naphthassuch as Naphthalite 66/3 and oxygenated solvents such as hydrocarbonethers, e.g., tetrahydrofuran and the dimethylether of ethylene glycol;ketones such as methyl isobutyl ketone and esters such as ethyl acetateand the like. Mixtures of organic solvents can also be used.

The components of the compositions of this invention can be mixed in anymanner such as in bulk or in organic solvent. Since the resinouscopolymer (A) is a solid and is conveniently prepared and handled in anorganic solvent, the preparation of the composition of this inventionpreferably uses an organic solvent, at least for the mixing of (A) and(B). The organic solvent can be any of the solvents recited above inconnection with component (E). The mixing of the components can beaccomplished by any of the techniques known in the art, such as milling,blending, stirring, and the like, either in batch or in continuousprocess.

The composition of this invention can be prepared, with or without theaid of solvent, by simply mixing (A), (B), (C), and (D) together in thestated proportions. The order of mixing of the components is notcritical, except that the organopolysiloxane (C) and the catalyst (D)are preferably brought together last. If heat is used in the preparationof the compositions of this invention, it is preferred to add theorganopolysiloxane (C) after all heating operations in the preparationprocess have been completed. The preceding system is referred to hereinas a one-component system. However, the best method of preparing thecomposition of this invention is based on a two-component system,wherein 2 blends are used, one comprising the resinous copolymer, whichmay be dissolved in about an equal weight of an organic solvent tofacilitate mixing, with polydiorganosiloxane (6) and the other blendcomprising the resinous copolymer, which also may be dissolved in aboutan equal weight of an organic solvent to facilitate mixing, withpolydiorganosiloxane (C), so as to form pre-made intermediates. Thismethod is preferred because it facilitates control of the SiH/SiVinylratio. To obtain compositions having at least 90 % and preferably about100% solids, the copolymer /polydiorganosiloxane blends should bedevolatilized under conditions equivalent to heating for 1 hour at 150°C. at atmospheric pressure in order to obtain optimum pressure sensitiveadhesive properties. Obviously, excessively high temperatures should beavoided when components (A) and (B) or their mixtures are beingdevolatilized. A temperature of 100° C., and preferably 80° C., shouldnot be exceeded. The mixture of (A), (B) and solvent is devolatilized inthin film at 70° C. at full vacuum. Additional solvent may be added tothe cooled, devolatilized mixtures to obtain a desired viscosity.Catalyst (D) is added to the devolatilized mixture of (A) and (B) tocomplete the composition of the first component of the two-componentsystem. The second mixture is prepared by blending (A), (C), and solventand then devolatilizing the blend under vacuum at a temperature of 70°C. A small amount of addition-cure inhibitor and additional solvent mayalso be added to the cooled, devolatilized mixture of (A) and (C) or (A)and (B) to obtain a desired viscosity. The final composition iscompleted by mixing the two components in appropriate amounts.

Thus, in a preferred embodiment of the composition of the presentinvention, the composition comprises by weight:

(1) a solventless mixture comprising by weight from about 55 to about 62parts by weight of (A) and from about 38 to about 45 parts by weight of(B);

(2) a solventless mixture comprising by weight from about 55 to about 62parts by weight of (A) and from about 38 to about 45 parts by weight of(C); and

(3) a hydrosilation catalyst.

Small amounts of additional ingredients may be added to the compositionof this invention if desired. For example, antioxidants, pigments,stabilizers, fillers, and the like, may be added as long as they do notmaterially reduce the pressure sensitive adhesive properties of thesecompositions. Volatile additives are preferably added after any solventremoval operations have been completed. In addition, a condensationcatalyst can be added which promotes and controls the reaction betweenthe silanol groups on the MQ resin and the available excess hydride.Such catalysts are known in the art and include, for example, organotincompounds, acidic species, amine compounds, as well as thosehydrosilation catalysts which are capable of functioning as condensationcatalysts, e.g., organoplatinum compounds. If used, the condensationcatalyst can be introduced only at certain stages, i.e., preferablyafter the hydrosilation reaction between the alkenyl radicals ofcomponent (B) and the silicon-bonded hydrogen atoms of (C) has occurredto a sufficient extent or to completion.

A long or longer "shelf life" can be obtained by mixing a platinumcatalyst inhibitor in either of the components in a two-component systemor in the curable mixture in the case of a one-component system.Platinum catalyst inhibitors which are useful in the composition of thisinvention and which display varying lengths of cure time inhibition inour compositions are those described in U.S. Pat. Nos. 3,188,299;3,188,300; 3,192,181; 3,344,111; 3,383,356; 3,445,420; 3,453,233;3,453,234; and 3,532,649, and others which might be known in the art.All of the patents cited in the instant paragraph are incorporated byreference herein. Concrete examples of inhibitors which can be used inthe composition of the present invention include the ene-ynes, such as3-methyl-3-pentene-l -yne and 3,5-dimethyl-3-hexene-l -yne; the alkynylalcohols, such as 3-methyl-1 -butyne-3-ol; 3,5-dimethyl-1 -hexyne-3-ol;3-methyl-1-pentyne-3-ol; and phenylbutynol; the unsaturated ester, suchas alkyl and substituted alkyl maleates; andpolymethylvinylcyclosiloxanes. The preferred inhibitors for use in thepresent invention are the dialkylmaleates and most preferablydimethylmaleate.

The effectiveness of a platinum catalyst inhibitor depends on manyfactors such as its chemical composition, its physical properties, itsconcentration, and the like. For the purposes of this invention, aneffective amount of any particular platinum catalyst inhibitor can bedetermined by routine experimentation. Since many platinum catalystinhibitors are relatively volatile it is preferable to add them to thecompositions of this invention after any heating and/or vacuumoperations of the preparative process have been completed. For maximumeffectiveness, however, a platinum catalyst inhibitor should be added tothe composition of this invention at least simultaneously with, an*dpreferably prior to the mixing of components (C) and (D) or partscontaining them.

As mentioned earlier herein, the present invention is based on thediscovery that a solventless or high solids-containing pressuresensitive adhesive composition having high tack and high peel adhesiveproperties can be obtained from low viscosity vinyl polymer inputs by(1) first effecting a hydrosilation reaction between (A), (B) and (C) inthe presence of (D), wherein the molar ratio of silicon-bonded hydrogengroups in (C) to silicon-bonded alkenyl groups in (B) (sometimesreferred to herein as the "SiH:SiVinyl" ratio) is within a criticalrange, and further wherein the hydroxy content of the resinous copolymer(A) is at a critical level, and (2) then effecting a condensationreaction between the hydroxyl radicals on the resinous copolymer (A) andthe excess terminal hydride radicals on (C).

The hydrosilation reaction can be carried out at temperatures rangingfrom about 70° C. to about 200° C. The condensation reaction between thehydroxyl radicals on the resinous copolymer (A) and the excess terminalhydride radicals on (C) can occur at a lower rate at 70° C. but occursmore readily at temperatures of 150° C. and above. Typically, thereactions are carded out by heating the mixture of components (A), (B),(C), and (D) and any optional ingredients to a temperature of 135° C. orhigher for a period of from about 3 to about 5 minutes. Alternatively,the mixture of components can first be heated to a relatively lowtemperature such that the hydrosilation reaction occurs readily whilethe condensation reaction occurs less readily, and then heated to ahigher temperature whereat the condensation reacts readily. Thereactions may also be carried out by heating components (A)-(D) and anyoptional ingredients to a temperature of about 125° C. or higher for atleast 5 minutes.

The condensation reaction imparts stability, and consequently greaterpeel adhesion and tack properties, to the cured pressure sensitiveadhesive composition. Thus, without the condensation reaction, apressure sensitive adhesive having less desirable tack and peel adhesionproperties will result.

Curing time is dependent on the SiH/SiVinyl molar ratio, the thicknessof the pressure sensitive adhesive, catalyst and inhibitor levels.Generally, at temperatures of 100°-150° C., a SiH/SiVinyl molar ratio ofabout 1.0:1, a PSA thickness of 1-4 mils, a catalyst level of 30 ppm andan inhibitor level of 0.5% by weight, cure time is no more than 5minutes. The temperature and time required to cure the compositions ofthis invention are also interdependent. Generally, the compositions ofthis invention will cure at a temperature of about 125° C. and higherfor a cure time of about 5 minutes to achieve the superior pressuresensitive adhesives of this invention. If shorter cure times aredesired, e.g., about 3 minutes, then the cure temperature is typically abit higher, i.e., about 135° C. Preferably, cure temperatures of fromabout 135° C. or higher for a cure time of up to about 5 minutes areused. The exceptional pressure sensitive adhesive characteristics ofthese compositions are developed when the composition is cured and thecured composition is essentially free of organic solvent.

Preferably, the uncured composition of this invention should be usedwithin a few hours after being prepared, although this time intervalfrom preparation to use, otherwise known as "shelf life", can beextended to several days by cooling the mixture to a temperature of -20°C. or below. Equally long or longer "shelf life" can be realized bymixing a platinum catalyst inhibitor such as any of those describedpreviously herein in either of the two components of a two-componentsystem or in the curable mixture in the case of a one-component system.

The uncured composition of this invention can be used as a solution inone or more of the organic solvents described above or the compositioncan be used with no solvent present. While it is possible to use as muchas 40 percent of an organic solvent based on the total weight of thecomposition, the presence of solvent is not required. If the presence ofsolvent is desired, this can be accomplished simply by not removing allof the solvent that is used in the preparation of the composition.Alternately, all of the solvent that is used in the preparation of thecomposition can be removed and the desired amount of the same or anothersolvent can be added. It will be obvious to those skilled in the artthat in the case where the solvent that is used to aid in theapplication of the composition of this invention has a higher boilingpoint than the solvent used in their preparation, the necessary solventchange can be accomplished in two steps as described above or in a onestep process wherein the higher boiling point solvent is present in themixture during the removal of the lower boiling solvent. If, during thepreparation of the composition of this invention, any portion of thesolvent is removed, particularly if heat and/or vacuum is used to removethe solvent, it is preferred to remove the solvent prior to the additionof other volatile components such as inhibitors or additives. Theremoval of solvent can be accomplished by any of the known techniquessuch as entrainment in a stream of inert gas, evaporation, distillation,thin film stripping, and the like, and at any combination of temperatureand pressure where the temperature is not allowed to exceedapproximately 200° C., preferably about 150° C.

The compositions of this invention are useful as pressure sensitiveadhesives and will readily stick to a solid support, whether flexible orrigid. The composition is simply applied to the surface of the supportby any suitable coating means such as rolling, spreading, spraying, andthe like; and cured as described above. It should be understood that theuse of the compositions of this invention encompasses not only theapplication of the completed, uncured composition on the surface. Forexample, it is within the scope of this invention to apply a layer of amixture of (A), (B), and (C) to a solid support and then add thehydrosilation catalyst (D), the needed mixing being accomplished bydimusion of (D) into the layer of (A), (B), and (C). It is preferred todelay the curing reaction until (D) is thoroughly diffused into thelayer on the support. Any solvent that is present in the curedcomposition is preferably allowed to evaporate before the surfacebearing the composition is adhered to a substrate, although this is notnecessary.

The surface of the support and the substrate to which the support isadhered may be any known solid material such as metals, e.g., aluminum,silver, copper, iron, and their alloys; porous materials such as paper,wood, leather, and fabrics; organic polymeric materials such aspolyolefins, e.g., polyethylene and polypropylene; fluorocarbon polymerssuch as polytetrafluoroethylene and polyvinylfluoride, siliconeelastomers, silicone resins, polystyrene; Nylon® polyamides, polyimides,polyesters, and acrylic polymers; painted surfaces; siliceous materialssuch as concrete, bricks, cinderblocks, and glass, e.g., glass cloth andthe like. Porous materials such as glass cloth are often impregnatedwith a substance that will prevent the migration of the PSA from onesurface to another surface of the support. It is also well known tochemically treat the surface of a fluorocarbon polymer support toenhance the adhesion of a PSA to said surface.

Solid supports bearing the cured compositions of this invention arereliably adhered to any solid substrate because the compositions possessthe desirable combination of high tack and good adhesive strength.

Useful articles which can be prepared with the PSAs of this inventioninclude pressure sensitive adhesive tapes, labels, emblems, and otherdecorative or informative signs, and the like. An especially usefularticle is one comprising a support, flexible or rigid, that canwithstand extreme temperatures, hot and/or cold, and carrying on atleast one surface thereof, the polyorganosiloxane PSAs of thisinvention. Such an article makes full use of the stability at hightemperatures and the flexibility at low temperatures that the PSAs ofthis invention possess.

A preferred article is a pressure sensitive adhesive tape comprising animpregnated glass cloth, a polyester polymer, a polyimide polymer or achemically treated fluorocarbon polymer support carrying on at least onesurface thereof the cured compositions of this invention.

In order that those skilled in the art may better understand the presentinvention, the following examples are given to illustrate but not tolimit the invention which is fully delineated by the appended claims.

Experimental

In the examples below, the term "MQ resin" refers to 60% by weightsolution in toluene of a silicone resin containing (CH₃)₃ SiO_(1/2)("M") units, and SiO_(4/2) ("Q") units and having a silanol content ofabout 1 to 3 % by weight and having a molar ratio of M units to Q unitsof 0.7:, and containing no alkenyl groups.

EXAMPLE 1

Example 1 illustrates the preparation of a pressure sensitive adhesivecomposition within the scope of the present invention.

Component A is a premade intermediate composition containing 54% byweight of a silicone MQ resin and 46% by weight of a low viscosity,vinyl-terminated polydimethylsiloxane having a viscosity of about 215centipoise at 25° C., a degree of polymerization of about 119.5 (or4,524 g rams/equivalent vinyl), a vinyl content of 0.6% by weight.

Component B is a premade intermediate composition containing 54% byweight of a silicone MQ resin and 46% by weight of a hydrogen-stoppedpolydimethylsiloxane having a hydride content of about 0.023% by weight,a degree of polymerization of 117 (or 4,405 grams/equivalent hydride),and a viscosity of 142 centipoise at 25° C.

The platinum catalyst used contains 4.5-5.5% by weight platinum complexcatalyst stabilized in solution in excess tetramethyldivinyldisiloxane.

A pressure sensitive adhesive was prepared by mixing 6.0 grams ofcomponent A, 10.0 grams of component B, 0.3% by weight of dimethylmaleate inhibitor, and 27 ppm of platinum catalyst based on the totalweight of the two pre-made intermediates referred to above. About 1.5grams of toluene was added to the mixture to yield a solids content ofabout 90% by weight.

The mixture was applied over a 1 mil thick polyethylene terephthalate(PET) film and cured at 125° C. for five minutes to yield a pressuresensitive adhesive having a thickness of 1.5-2.0 mil.

The peel adhesion of the pressure sensitive adhesive was determinedusing a Scott Tester, using 180° pull at a rate of 12 inches/minuteagainst a stainless steel plate. Tack was measured by means of a PolykenProbe Tack Tester, manufactured by Testing Machines Incorporated, whichwas fitted with a probe having a diameter of 0.5 centimeter and operatedat a rate of 1 cm/sec and a dwell time of 1 second. A summary of dataregarding MQ resin level, hydride/vinyl ratio, vinyl chain length, andhydride chain length for the samples prepared in Example 1 is providedin Table 1 below.

EXAMPLES 2-7

In Examples 2-7, five samples were prepared according to the procedurefollowed in Example 1, except that the MQ resin level, hydride/vinylratio and hydride chain length (represented by "D" which indicatesdegree of polymerization) varied as indicated in Table 1 below. Thecompositions prepared in Examples 2-6 had a solids content of about 95%by weight.

A summary of data regarding MQ resin level, hydride/vinyl ratio, vinylchain length, and hydride chain length for the samples prepared inExamples 2-7 is provided in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        Examples 1-7: Formulations                                                           MQ Resin  Hydride/ Vinyl Chain                                                                            Hydride Chain                              Example                                                                              Level     Vinyl    Length   Length                                     No.    (Weight %)                                                                              Ratio    (D units)                                                                              (D units)                                  ______________________________________                                        1      54.00     1.70     120.00   117.00                                     2      54.00     2.20     120.00   117.00                                     3      54.00     2.64     120.00   117.00                                     4      57.00     2.63     120.00   128.00                                     5      58.00     1.01     120.00   128.00                                     6      58.00     4.28     120.00   117.00                                     7      58.00     1.55     120.00   117.00                                     ______________________________________                                    

The peel adhesion, tack properties, and quality of cure of the samplesprepared in Examples 1-7 are shown in Table 2 below.

                  TABLE 2                                                         ______________________________________                                        Examples 1-7: Properties                                                      Example   Probe Tack                                                                              Peel Adhesion Quality                                     No.       (g/cm.sup.2)                                                                            (ounces/inch) of Cure                                     ______________________________________                                        1         708       30            Cured Well                                  2         680       30            Cured Well                                  3         860       38            Cured Well                                  4         665       33            Cured Well                                  5         340       14            Residues,                                                                     Poor Cure                                   6         607       40            Cured Well                                  7         492       34            Cured Well                                  ______________________________________                                    

The peel adhesion and tack data provided in Table 2 above shows thatSiH/SiVinyl ratios which are too low result in pressure sensitiveadhesives having significantly lower tack and peel adhesion propertiesthan those prepared using SiH/SiVinyl ratios within the range of thepresent invention.

EXAMPLE 8

To 5.71 grams of a solventless premade blend containing 58% by weight ofMQ resin and 42% by weight of vinyl-stopped silicone fluid (120 "D"units) were added 6.2 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (1 28 "D" units), 0.6 grams of toluene, 0.035 grams of dimethylmaleate, and 50 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 1.01/1. The mixture was coated over a 1mil thick PET tape and cured at 150° C. for 3 minutes, to form anadhesive having a thickness of 1.6 mil.

The adhesive exhibited a gummy feel and left residues over a steelplate, indicating a poorly cured structure. The probe tack was 340grams/cm²., and the peel adhesion was 14 ounces/inch with cohesivefailure.

EXAMPLE 9

To 3.25 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (120 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (1 28 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 50 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 2.63/1. The mixture was coated over a 1mil thick unprimed PET tape and cured at 150° C. for 3 minutes, to forman adhesive having a thickness of 1.7 mil.

The adhesive formed a well cured residue-free tape and had a tack of 665grams/cm² and a peel adhesion of 33 ounces/inch.

EXAMPLE 10

To 7.77 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (1 20 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (1 28 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 20 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 1. 10/1. The mixture was coated over a 1mil thick unprimed PET tape and cured at 125° C. for 3 minutes, to forman adhesive having a thickness of 1.8 mil.

EXAMPLE 11

The procedure described in Example 10 was repeated except that the curedcomposition was further subjected to post cure at 165° C. for 2 minutes.

EXAMPLE 12

To 3.25 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (120 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (128 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 26 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 2.63/1. The mixture was coated over a 1mil thick unprimed PET tape and cured at 125° C. for 3 minutes, to forman adhesive having a thickness of 1.7 mil.

EXAMPLE 13

The procedure described in Example 12 was repeated except that the curedcomposition was further subjected to post cure at 165° C. for 2 minutes.

EXAMPLE 14

To 1.42 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (1 20 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (128 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 30 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 6/1. The mixture was coated over a 1 milthick unprimed PET tape and cured at 125° C. for 3 minutes, to form anadhesive having a thickness of 1.6 mil.

EXAMPLE 15

The procedure described in Example 14 was repeated except that the curedcomposition was further subjected to post cure at 165° C. for 2 minutes.

EXAMPLE 16

To 0.85 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (120 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (1 28 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 32 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 10/1. The mixture was coated over a 1 milthick unprimed PET tape and cured at 125° C. for 3 minutes, to form anadhesive having a thickness of 1.5 mil.

EXAMPLE 17

The procedure described in Example 14 was repeated except that the curedcomposition was further subjected to post cure at 165° C. for 2 minutes.

EXAMPLE 18

To 0.71 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (120 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (1 28 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 33 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 12/1. The mixture was coated over a 1 milthick unprimed PET tape and cured at 125° C. for 3 minutes, to form anadhesive having a thickness of 1.9 mil.

EXAMPLE 19

The procedure described in Example 14 was repeated except that the curedcomposition was further subjected to post cure at 165° C. for 2 minutes.

EXAMPLE 20

To 0.57 grams of a solventless premade blend containing 54% by weight ofMQ resin and 46% by weight of vinyl-stopped silicone fluid (1 20 "D"units) were added 10.0 grams of a solventless premade blend containing58% by weight of MQ resin and 42% by weight of hydride-stopped siliconefluid (1 28 "D" units), 0.7 grams of toluene, 0.035 grams of dimethylmaleate, and 33 ppm of platinum catalyst. The calculated hydride/vinylratio for this composition was 15/1. The mixture was coated over a 1 milthick unprimed PET tape and cured at 125° C. for 3 minutes, to form anadhesive having a thickness of 1.9 mil.

EXAMPLE 21

The procedure described in Example 14 was repeated except that the curedcomposition was further subjected to post cure at 165° C. for 2 minutes.

Data regarding MQ resin level, hydride/vinyl ratio, cure time andtemperature, and post-cure time and temperature for Examples 10-21 aresummarized in Table 3 below. The term "yes" in Table 3 means that thesample was cured and/or post-cured as described hereinabove andindicated in the heading to the column under which the term is found.The term "no" means that the sample was not cured and/or post-cured asindicated in the relevant column.

                  TABLE 3                                                         ______________________________________                                        Examples 10-21: Formulations                                                          MQ Resin  Hydride/  Cure    Post-Cure                                 Example Level     Vinyl     (125° C.,                                                                      (165° C.,                          No.     (Weight %)                                                                              Ratio     3 minutes)                                                                            2 minutes)                                ______________________________________                                        10      56.20     1.10      Yes     No                                        11      56.20     1.10      Yes     Yes                                       12      57.00     2.63      Yes     No                                        13      57.00     2.63      Yes     Yes                                       14      57.50     6         Yes     No                                        15      57.50     6         Yes     Yes                                       16      57.70     10        Yes     No                                        17      57.70     10        Yes     Yes                                       18      57.70     12        Yes     No                                        19      57.70     12        Yes     Yes                                       20      57.80     15        Yes     No                                        21      57.80     15        Yes     Yes                                       ______________________________________                                    

The peel adhesion and tack properties and the quality of cure of thesamples prepared in Examples 10-21 were determined and are presented inTable 4 below.

                  TABLE 4                                                         ______________________________________                                        Examples 10-21: Properties                                                    Example Tack        Peel Adhesion                                             No.     (grams/cm.sup.2)                                                                          (ounces/inch)                                                                             Quality of Cure                               ______________________________________                                        10      380         12          Under Cured,                                                                  gummy residues                                11      332         15          Under Cured,                                                                  gummy residues                                12      406         19          Under Cured,                                                                  gummy residues                                13      714         29          Well Cured, No                                                                Residue                                       14      322         14          Under Cured,                                                                  gummy residues                                15      504         27          Well Cured, No                                                                Residue                                       16      362         13          Under Cured,                                                                  gummy residues                                17      222         27          Well Cured, No                                                                Residue                                       18      348         11          Under Cured,                                                                  gummy residues                                19      270         26          Well Cured, No                                                                Residue                                       20      372         11          Under Cured,                                                                  gummy residues                                21      254         24          Well Cured, No                                                                Residue                                       ______________________________________                                    

Examples 10-17 illustrate the benefit of having a cure reaction occurbetween the silanol groups on the MQ resin and the terminal hydridegroups on the hydride polymer. The films prepared in Examples 10, 12,14, and 16 were only cured at 125° C. for 3 minutes while those preparedin Examples 11, 13, 15, and 17 were cured at 125° C. for 3 minutes andthen post-cured at 165° C. for 2 minutes. The primary reaction at 125°C. was a hydrosilation reaction between vinyl groups on the vinylpolymer and hydride groups on the hydride polymer. There is only aslight reaction at this temperature between the hydride groups on thehydride polymer and the silanol groups associated with the MQ resin.However, after post-cure at 165° C., good cure and adhesive propertieswere obtained due to the reaction between the silanol groups associatedwith the MQ resin and available hydrides on the hydride polymer.

The results obtained for Examples 10-17 further indicate that at ahydride/vinyl ratio of 1.1/1 or less, insufficient reaction occurs,resulting in poor cure.

What is claimed is:
 1. An article of manufacture comprising a solid support carrying on at least one surface thereof an organopolysiloxane composition curable to produce a pressure sensitive adhesive having high tack and high peel adhesion, consisting essentially of by weight;(A) from about 50 to about 75 parts by weight of a toluene soluble, resinous copolymer comprising R₃ SiO_(1/2) units and SiO_(4/2) units wherein R is a monovalent hydrocarbon radical having from 1 to about 6 carbon atoms, wherein the resinous copolymer comprises from about 0.2% to about 5.0% by weight, based on the total weight of the copolymer, of hydroxyl radicals, at least 95% of all R groups being an alkyl group, the total number of R radicals that are alkenyl radicals being 0-0.5% of all R radicals, the molar ratio of R₃ SiO_(1/2) units to SiO_(4/2) units being from about 0.6 to about 0.9 inclusive; (B) an alkenyl-terminated polydiorganosiloxane having a viscosity of from about 10 to about 500 centipoise at 25° C. and having the general formula

    R.sup.2 R.sup.1.sub.2 SiO(R.sup.3.sub.2 SiO).sub.m SiR.sup.1.sub.2 R.sup.2 ( 1)

wherein each R¹ is independently an alkyl group having from 1 to about 10 carbons atoms or an aryl group, R² is an alkenyl group having from 1 to about 10 carbon atoms, each R³ is independently R¹ or R², with the proviso that at least 99.5% of all R³ radicals are R¹, "m" is a number in the range of from about 1 to about 300; (C) a hydride-terminated organohydrogenpolysiloxane compatible with the mixture of (A) and (B) and having a viscosity of from about 10 to about 1,000 centipoise at 25° C. and having the general formula

    R.sup.4.sub.2 HSiO(R.sup.5.sub.2 SiO).sub.a SiHR.sup.4.sub.2 ( 11)

wherein each R⁴ is independently an alkyl group having from 1 to about 10 carbons atoms or an aryl group, and each R⁵ is hydrogen or R⁴, with the proviso that at least 99.5% of all R⁵ radicals are R⁴, "a" is a number in the range of from 1 to about 500, there being at least two silicon-bonded hydrogen atoms per molecule of (C), no silicon atom bearing more than one silicon-bonded hydrogen atom; the total of (B) and (C) being from about 25 to about 50 parts by weight; the total of (A), (B), and (C) being 100 parts by weight; the molar ratio of silicon-bonded hydrogen groups in (C) to silicon-bonded alkenyl groups in (A) and (B) being in the range of from about 1.2:1 to about 15.0:1; (D) a catalytic amount of hydrosilation catalyst; and (E) from 0 to about 40% by weight of an organic solvent.
 2. An article of manufacture of claim 1 wherein the composition on at least one surface thereof is cured.
 3. A pressure sensitive adhesive tape of claim 1 wherein the composition on at least one surface thereof is cured.
 4. A pressure sensitive adhesive tape according to claim 3 wherein the flexible support is an impregnated glass cloth, a polyester polymer, a polyimide polymer, or a chemically treated fluorocarbon polymer support.
 5. An article according to claim 1 wherein the amount of organic solvent (E) is from about 0 to about 20% by weight.
 6. An article according to claim 1 wherein the amount of organic solvent (E) is 0% by weight
 7. An article according to claim 1 wherein the ratio of silicon-bonded hydrogen atoms in (C) to olefinically unsaturated radicals in the total of (A) and (B) is in the range of from about 1.25:1 to about 6:1.
 8. An article according to claim 7 wherein the ratio of silicon-bonded hydrogen atoms in (C) to olefinically unsaturated radicals in the total of (A) and (B) is in the range of from about 1.35:1 to about 4.5:1.
 9. An article according to claim 1 wherein R is a monovalent hydrocarbon radical having from 1 to about 6 carbons and selected from the group consisting essentially of alkyl radicals; cycloaliphatic radicals; olefinic radicals; and phenyl radicals.
 10. An article according to claim 9 wherein R is methyl.
 11. An article according to claim 1 wherein R¹ and R³ are each a methyl radical.
 12. A composition according to claim 1 wherein R² is vinyl.
 13. An article according to claim 1 wherein R⁴ and R⁵ are each a methyl radical.
 14. An article according to claim 1 wherein the resinous copolymer (A) comprises from about 1.0% to about 3.0% by weight, based on the total weight of the copolymer, of hydroxyl radicals.
 15. An article according to claim 14 wherein the resinous copolymer (A) comprises from about 1.5% to about 2.5% by weight, based on the total weight of the copolymer, of hydroxyl radicals.
 16. An article according to claim 1 wherein (B) has a viscosity of from about 100 to about 300 centipoise at 25° C.
 17. An article according to claim 1 wherein (C) has a viscosity of from about 20 to about 750 centipoise at 25° C.
 18. An article according to claim 17 wherein (C) has a viscosity of from about 100 to about 400 centipoise at 25° C.
 19. An article according to claim 1 wherein (A) is present in the amount of from about 50 to about 70 parts by weight.
 20. An article according to claim 19 wherein (A) is present in the amount of from about 55 to about 62 parts by weight.
 21. An article according to claim 1 wherein the total amount of (B) and (C) is from about 30 to about 50 parts by weight.
 22. An article according to claim 21 wherein the total amount of (B) and (C) is from about 38 to about 45 parts by weight.
 23. An article according to claim 1 wherein the hydrosilation catalyst is a platinum-containing catalyst.
 24. An article according to claim 23 wherein the platinum-containing catalyst is a platinum complex catalyst stabilized in solution in excess tetramethyldivinyldisiloxane.
 25. An article according to claim 1 wherein the curable composition further comprises an inhibitor for the hydrosilation catalyst.
 26. An article according to claim 25 wherein the inhibitor is a dialkylmaleate.
 27. An article according to claim 26 wherein the dialkylmaleate is dimethylmaleate.
 28. An article according to claim 1 wherein (B) has a viscosity of about 10 to about 400 centipoise at 25° C.
 29. A pressure sensitive adhesive tape comprising a flexible support carrying on at least one surface thereof an organopolysiloxane composition curable to produce a pressure sensitive adhesive having high tack and high peel adhesion, consisting essentially of weight;(A) from about 50 to about 75 parts by weight of a toluene soluble, resinous copolymer comprising R₃ SiO_(1/2) units and SiO_(4/2) units wherein R is a monovalent hydrocarbon radical having from 1 to about 6 carbon atoms, wherein the resinous copolymer comprises from about 0.2% to about 5.0% by weight, based on the total weight of the copolymer, of hydroxyl radicals, at least 95% of all R groups being an alkyl group, the total number of R radicals that are alkenyl radicals being 0-0.5% of all R radicals, the molar ratio of R₃ SiO_(1/2) units to SiO_(4/2) units being from about 0.6 to about 0.9 inclusive; (B) an alkenyl-terminated polydiorganosiloxane having a viscosity of from about 10 to about 500 centipoise at 25° C. and having the general formula

    R.sup.2 R.sup.1.sub.2 SiO(R.sup.3.sub.2 SiO).sub.m SiR.sup.1.sub.2 R.sup.2 ( 1)

wherein each R¹ is independently an alkyl group having from 1 to about 10 carbon atoms or an aryl group, R² is an alkenyl group having from 1 to about 10 carbon atoms, each R³ is independently R¹ or R² with the proviso that at least 99.5% of all R³ radicals are R¹, "m" is a number in the range of from about 1 to about 300; (C) a hydride-terminated organohydrogenpolysiloxane compatible with the mixture of (A) and (B) and having a viscosity of from about 10 to about 1,000 centipoise at 25° C. and having the general formula

    R.sup.4.sub.2 HSiO(R.sup.5.sub.2 SiO).sub.a SiHR.sup.4.sub.2 ( 11)

wherein each R⁴ is independently an alkyl group having from 1 to about 10 carbon atoms or an aryl group, and each R⁵ is hydrogen or R⁴, with the proviso that at least 99.5% of all R⁵ radicals are R⁴, "a" is a number in the range of from 1 to about 500, there being at least two silicon-bonded hydrogen atoms per molecule of (C), no silicon atom bearing more than one silicon-bonded hydrogen atom; the total of (B) and (C) being from about 25 to about 50 parts by weight; the total of (A), (B), and (C) being 100 parts by weight; the molar ratio of silicon-bonded hydrogen groups in (C) to silicon-bonded alkenyl groups in (A) and (B) being in the range of from about 1.2:1 to about 15.0:1; (D) a catalytic amount of a hydrosilation catalyst; and (E) from 0 to about 40% by weight of an organic solvent.
 30. A pressure sensitive adhesive tape according to claim 29 wherein the flexible support is an impregnated glass cloth, a polyester polymer, a polyimide polymer, or a chemically treated fluorocarbon polymer support. 